CARET is an ongoing double-blind lung cancer chemoprevention trial of the efficacy and safety of the combination of 30 mg beta- carotene and 25,000 IU retinyl palmitate daily in two high-risk populations: (a) male and female current and former smokers recruited primarily from insurance-based sources, and (b) males with extensive occupational asbestos exposure recruited primarily from employment-based sources. We have documented successful recruitment, excellent compliance, and minimal side effects in over 15,000 participants randomized thus far at six study centers. Through April 30, 1993, CARET has randomized 4,000 asbestos-exposed workers, exceeding accrual goals at all five CARET asbestos centers, and 11,105 heavy smokers. Seattle and Portland have exceeded their heavy smoker goals, and Irvine is on track to achieve its goal in July 1994. During the final five-year period, CARET will focus on retention, adherence to protocol, ascertainment of endpoints, monitoring of key design parameters, closeout of the trial, and analysis and publication. Projections indicate that with 14,240 smokers and 4,010 asbestos-exposed participants and 114,100 person-years of follow-up through February 1998, CARET will be capable of detecting a 23% reduction in lung cancer incidence in the two high-risk populations combined, and 27%, 49%, 32%, and 35% reductions in the smokers, female smokers, male smokers, and asbestos-exposed subgroups, respectively. The San Francisco (SF) Study Center recruited its first asbestos- exposed participants in February 1989 and reached its randomization goal of 804 in September 1992. Recruitment was primarily through trade unions and attorneys specializing in asbestos-related disease cases. In January 1993, the SF Study Center began recruiting heavy-smoker participants, spouses or partners of randomized asbestos-exposed participants. Through April 30, 1993, the SF study center has randomized a total of 847 participants, 845 asbestos- exposed workers and 2 heavy-smoker spouses. During the final five years of CARET, the SF Study Center will focus on retention o participants, maintenance of adherence to protocol, improvement of data quality, and collection of endpoint data. Because long-term retention of participants is critical for the success of CARET, we will undertake the following efforts during the proposed funding period: maintain the existing participant advisory committee, produce a study center-specific newsletter, distribute daily-use gifts as tokens of appreciation, and continue t provide travel expense reimbursement as needed. Specific preparations for study closeout and collaboration in analysis of data and publication of the final results will occur during the final two years.